Substrate processing apparatus and method

ABSTRACT

A substrate processing apparatus, comprising a substrate support ( 32 ) provided with a support surface ( 34 ) for supporting a substrate or a substrate carrier ( 24 ) thereon and a support heater ( 50 ) constructed and arranged to heat the support surface ( 34 ). The apparatus comprises a heat shield constructed and arranged to cover and shield the substrate support ( 32 ) when no substrate or substrate carrier ( 24 ) is on the support surface.

FIELD

The present disclosure relates to the field of substrates processing apparatus and method. More in particular, the disclosure relates to a substrate processing apparatus comprising: a substrate support provided with a support surface for supporting a substrate or a substrate carrier thereon and a support heater constructed and arranged to heat the support surface, and to a method of using such an apparatus.

BACKGROUND

The simultaneous processing of a plurality of substrates (e.g., semiconductor wafers) in a vertical batch furnace presents the problem of how to subject all wafers that are stacked into a substrate carrier (e.g., wafer boat) to substantially the same process conditions across their respective surface areas. One such process condition is the temperature uniformity. To obtain uniform processing results across the wafers of a batch, each of the wafers thereof may preferably be heated substantially uniformly to a common temperature by heating means disposed proximate a side wall of the process chamber and proximate a top wall of the process chamber.

As regards in particular to the upper wafers in the substrate boat, the wafer-to-wafer temperature uniformity is generally not a significant problem, while the within-wafer temperature uniformity (due to asymmetries in the construction of the furnace) may be enhanced by an optional boat rotation mechanism. However, in a vertical batch furnace, the temperature uniformity of the lower wafers in the wafer boat may prove difficult to control. This may be due to the fact that they are located closely to the relatively cold lower door zone of the furnace. To mitigate the effect of their location, a pedestal supporting the wafer boat from below may be provided with a support heater for heating the lower wafers.

The support heater may heat up the substrate support and surroundings also when it is not needed. The later may occur when the substrates in the substrate support may be moved out of the reactor to cool down and to replace the substrates with the wafer handler. This heating may lead to non-uniform heating of the substrate support, slower cooldown of the substrates in the substrate support, and/or distortion of the airflow during handling of the substrates.

It is therefore desirable to provide for an improved substrate processing apparatus.

SUMMARY

This summary is provided to introduce a selection of concepts in a simplified form. These concepts are described in further detail in the detailed description of example embodiments of the disclosure below. This summary is not intended to identify key features or essential features of the claimed subject matter, nor is it intended to be used to limit the scope of the claimed subject matter.

According to an embodiment there is provided an improved substrate processing apparatus. The substrate processing apparatus comprises a substrate support provided with a support surface for supporting a substrate or a substrate carrier thereon and a support heater constructed and arranged to heat the support surface. The apparatus comprises a heat shield constructed and arranged to cover and shield the substrate support when no substrate or substrate carrier is on the support surface.

According to a further embodiment there is provided a method comprising:

exchanging at least one substrate of the substrate carrier, while covering the substrate support with the heat shield while heating the support surface of the substrate support with the support heater;

moving the substrate support and the heat shield with respect to each other so as to support the substrate carrier on the support surface; and,

moving the substrate in the substrate carrier into a reactor.

For purposes of summarizing the invention and the advantages achieved over the prior art, certain objects and advantages of the invention have been described herein above. Of course, it is to be understood that not necessarily all such objects or advantages may be achieved in accordance with any particular embodiment of the invention. Thus, for example, those skilled in the art will recognize that the invention may be embodied or carried out in a manner that achieves or optimizes one advantage or group of advantages as taught or suggested herein without necessarily achieving other objects or advantages as may be taught or suggested herein.

All of these embodiments are intended to be within the scope of the invention herein disclosed. These and other embodiments will become readily apparent to those skilled in the art from the following detailed description of certain embodiments having reference to the attached figures, the invention not being limited to any particular embodiment(s) disclosed.

BRIEF DESCRIPTION OF THE DRAWINGS

While the specification concludes with claims particularly pointing out and distinctly claiming what are regarded as embodiments of the invention, the advantages of embodiments of the disclosure may be more readily ascertained from the description of certain examples of the embodiments of the disclosure when read in conjunction with the accompanying drawings, in which:

FIG. 1 is a schematic cross-sectional side view of a vertical batch furnace that includes a rotatable pedestal-heater-combination;

FIG. 2 is an enlarged cross-sectional side view of the pedestal section of the vertical batch furnace shown in FIG. 1;

FIGS. 3a to 3d schematically illustrate an exemplary vertical thermal furnace according to an embodiment; and,

FIG. 4 schematically illustrates another exemplary vertical thermal furnace according to a further embodiment.

DETAILED DESCRIPTION

Although certain embodiments and examples are disclosed below, it will be understood by those in the art that the invention extends beyond the specifically disclosed embodiments and/or uses of the invention and obvious modifications and equivalents thereof. Thus, it is intended that the scope of the invention disclosed should not be limited by the particular disclosed embodiments described below. The illustrations presented herein are not meant to be actual views of any particular material, structure, or device, but are merely idealized representations that are used to describe embodiments of the disclosure.

As used herein, the term “substrate” or “wafer” may refer to any underlying material or materials that may be used, or upon which, a device, a circuit, or a film may be formed. The term “semiconductor device structure” may refer to any portion of a processed, or partially processed, semiconductor structure that is, includes, or defines at least a portion of an active or passive component of a semiconductor device to be formed on or in a semiconductor substrate. For example, semiconductor device structures may include, active and passive components of integrated circuits, such as, for example, transistors, memory elements, transducers, capacitors, resistors, conductive lines, conductive vias, and conductive contact pads.

FIGS. 1 and 2 schematically illustrate in a cross-sectional side view a vertical thermal processing furnace or reactor 1. The furnace 1 may be of a single tube type and may include a generally bell jar-shaped reaction tube 10. The reaction tube 10 may delimit a reaction chamber 12 defining a reaction space 14 in which substrates e.g., wafers may be processed.

The reaction tube 10 may be encircled or surrounded by a tube heater for heating wafers received in the reaction space 14, such as an electrically resistive heating coil 18 that is powered by an electrical power supply (not shown). The tube heater 18 may be secured to a thermally insulating sleeve 16 that surrounds or encircles the reaction tube 10. The reaction tube 10 may have a generally tubular, for example circular or polygonal, cross-sectional shape, and extend along a central axis L. As regards the manufacturing material, the reaction tube 10 may be made of quartz, silicon carbide, silicon or another suitable heat resistant material. At its lower, open end, the reaction tube 10 may be supported on a flange 20 that defines a central furnace opening 22 via which a wafer boat 24 may enter and/or exit the reaction chamber 12.

The wafer boat 24 (substrate carrier), which may include a plurality of slots 26 (e.g., between 10 and 300, preferably between 25 and 250) for holding equally many semiconductor wafers 28 (only one of which is shown in FIGS. 1 and 2), may be supported on a support surface 34 of a substrate support 32 (e.g., pedestal of a support assembly 30). The substrate support 32 may be mounted on a doorplate or seal cap 42 by means of a bearing, e.g., a roller-, fluid- or magnetic bearing. An elevator or lift (not shown) may be used so that the substrate support 32 and the wafer boat 24 can be raised into and lowered from the reaction chamber 12 at the beginning and end of a treatment, respectively. To ensure that the reaction chamber 12 can be sealed in a gas-tight manner, several elastomeric O-rings 46 may be employed in the lower part of the furnace 1, in particular between the reaction tube 10 and the flange 20, and between the flange 20 and the door plate 42.

The substrate support 32 may be at least partly filled with a thermally insulating material 38, enabling it to serve as a heat shield for both the door plate 42 and the flange 20, and to reduce heat loss via the lower portion of the furnace 1. The insulating material 38 rests on a bottom plate 39, which is moveable (rotatable) relative to the walls of container 36. The substrate support 32 may further accommodate a support heater 50.

Underneath the support surface 34, the support heater 50 may spread out to cover an area that is approximately equal to the area of the support surface 34 in order to be able to heat (the lower) wafers 28 in the wafer boat 24 across their entire surface. In the depicted embodiment, the heater is fixedly connected to the insulating material 38 and the bottom plate 39. An upwardly extending connection portion 52 for (electrically) connecting to the support heater 50 is embedded in the thermally insulating material 38, while the horizontally extending portion rests thereon.

A motor drive may be provided to rotate the substrate support 32 around the central axis L of the reaction chamber 12. Since the wafer boat 24 is rigidly connected to the substrate support 32, it will rotate in unison therewith. The door plate 42 and the rest of the fixed structure of the furnace 1, e.g., the reaction tube 10 and the thermally insulating sleeve 16, remain stationary during rotation of container 36 of the substrate support 32. Bottom plate 39, insulating material 38 and support heater 50 preferably also remain stationary during rotation of container 36. This may in particular be done by fixedly or rigidly connecting bottom plate 39 with insulating material 38 and support heater 50 to a stationary part of the furnace 1 that is non-rotatably mounted with respect to the rotation axis L of the substrate support 32, such as the doorplate 42.

The substrate support 32 may comprise an upper plate, a cylindrical side plate and a bottom plate, which plates may be interconnected to define a generally cylindrical container 36. An outer surface of the upper plate may define the support surface 34 of the substrate support 30. The container 36 may define a body that extends between the upper plate and the bottom plate, which body accommodates at least part of the support heater 50.

The body of the cylindrical container 36 may further accommodate thermally insulating material 38. The support heater 50 may be disposed adjacent the upper plate, and the thermally insulating material 38 may be disposed below the support heater 50 which may rest on the thermally insulating material 38.

Alternatively, the support heater 50 may be rotatably mounted. In such a case, the rotary motion of the support heater 50 may be mechanically coupled to that of the substrate support 32, for example by means of a gear mechanism or fluid coupling with an appropriate gear/speed ratio that ensures that the substrate support 32 will rotate relative to the support heater 50. A rotatably mounted support heater 50 may also be provided with a dedicated motor drive that is configured to rotate the support heater at a different angular velocity than that at which the substrate support 32 is driven.

The support heater 50 may heat up the substrate support and surroundings also when it is not needed. The later may occur when the substrates in the substrate support 32 may be moved out of the reactor with the elevator (not shown) to cool down and to replace the substrates with the wafer handler (not shown). This heating up may lead to non-uniform heating of the substrates 28, because the support heater 50 may be heating up the lower part of the substrate carrier, e.g., wafer boat 24 and the substrates 28 in the lower part, already during loading of the substrates. Also cooldown of the substrates 28 in the substrate carrier (e.g., wafer boat 24) may be much slower because of the support heater 50 being hot. The airflow during handling of the substrates may also be distorted by the support heater 50 being hot. For example there may be created an upward flow by the hot substrate support while a downward flow may be preferred to avoid particle contamination on the substrates. Temporary switching off the support heater 50 may not be a viable solution because that may lead to an increase of the heating up times.

FIGS. 3a to 3d schematically illustrate an exemplary vertical thermal furnace according to an embodiment in which a heat shield constructed and arranged to cover and shield the substrate support when no substrate or substrate carrier is on the support surface may be moved over the substrate support 32. In order not to obscure the discussion of FIGS. 3a to 3d , same reference numerals as in FIGS. 1 and 2 are used for similar components. It is understood, however, that the physical properties of, and relationships between, the various components depicted in FIGS. 3a to 3d may differ from those in FIGS. 1 and 2. Other components of the vertical thermal furnace shown in FIGS. 3a to 3d may generally be identical to corresponding components of the above-described conventional furnace 1. The present embodiment may now be elucidated in general terms, with reference to the exemplary vertical furnace of FIGS. 3a to 3d . With the heat shield heating up of the substrate carrier and the surroundings of the substrate support 32 may be circumvented when no substrate 28 or substrate carrier 24 is on the support surface.

In FIG. 3a , substrates in the substrate carrier 24 supported on the substrate support 32 may be processed in the reaction chamber 12. The reaction chamber 12 may be closed with the door plate 42 and the substrates may be heated with the tube heater (not shown) and the support heater 50. After the substrates 28 have been processed in the reaction chamber 12 the substrates in the substrate support 32 may be moved out of the reaction chamber 12 to cool down (see FIG. 3b ). The apparatus may therefor comprise an actuator constructed and arranged to move at least one of the heat shield and the substrate support 32 with respect to each other. For example, the apparatus may comprise an elevator 59 constructed and arranged to move the substrate support 32 in a vertical direction. The elevator 59 may have a moving portion 63 which may be moveable along a spindle 65 driven by a motor 67.

As shown in FIG. 3c , the substrate carrier 24 may be completely moved out of the reaction chamber 12 with the elevator. Subsequently the reaction chamber 12 may be closed with a reaction chamber door 35. With the reaction chamber door 35 closed, it may be easier to keep the reaction chamber 12 at the correct temperature while not heating the surroundings (including the substrate carrier e.g., wafer boat 24 in the cool down position).

The substrate carrier 24 may be separated from the substrate support 32, as shown in FIG. 3d . The substrate support 32 may be covered with a heat shield 57. The apparatus may comprise a mover constructed and arranged to move at least one of the heat shield 57 and the substrate support 32 in a horizontal direction to cover and shield the substrate support 32. The heat shield 57 may cover and shield the substrate support 32 when no substrate or substrate carrier 24 is on the support surface 34. Heating up of the substrate carrier 24 and the surroundings of the substrate support 32 may be circumvented when no substrate 28 or substrate carrier 24 is on the support surface 34 by the heat shield 57.

The heat shield 57 may at least partially form a chamber constructed and arranged to store the substrate support 32 therein. The chamber may be substantially airtight to keep the heat within the chamber. The heat shield may comprise a thermally insulating material thermally insulating the substrate support 32 from the substrate carrier 24 and the surroundings of the substrate support 32.

The doorplate 42 of the furnace may form a part of the chamber. The heat shield may comprise an upper shield and a cylindrical side shield, which shields are interconnected to define a generally cylindrical chamber to cover and shield the substrate support 32 when no substrate or substrate carrier 24 is on the support surface. The opening of the generally cylindrical chamber may be closed with the doorplate 42 of the furnace.

FIG. 4 schematically illustrate an exemplary vertical thermal furnace according to a further embodiment in which a heat shield constructed and arranged to cover and shield the substrate support when no substrate or substrate carrier is on the support surface may be moved over the substrate support 32. In order not to obscure the discussion, same reference numerals as in FIGS. 1-3 are used for similar components. It is understood, however, that the physical properties of, and relationships between, the various components depicted in FIG. 4 may differ from those in FIGS. 1-3.

FIG. 4 discloses an apparatus comprising a recess 69 which may be closed with the heat shield 57 to form the chamber constructed and arranged to store the substrate support 32 therein. The recess 69 and the heat shield 57 may thermally insulate the substrate support 32 from the substrate carrier 24 and the surroundings of the substrate support 32.

In apparatus 1 of FIG. 1, the substrate support assembly 30 may include a substrate support 32 that may be rotatably mounted with respect to an (imaginary) rotation axis L. The substrate support 32 may include a generally cylindrical container 36 that is centered around the rotation axis L. The container 36 may include an upper wall, a cylinder jacket-shaped side wall, and a bottom wall, which walls are interconnected to form the container 36. The upper wall and the bottom wall may preferably be substantially flat. The upper wall of the container 36 may provide for an outer, upward facing substrate support surface 34. The rotation axis L may extend through this substrate support surface 34, and preferably be perpendicular thereto.

The body of the container, extending between the upper wall and the bottom wall, may define two body parts. A first body part, adjacent the upper wall, may define an interior space for receiving a heat generating portion of the support heater 50. A second body, adjacent the bottom wall, may define an interior annular space around the rotation axis L that may be filled with a thermally insulating material 38. The thermally insulating material may be in stationary, non-rotating relationship with the container 36.

The container 36 may further define a hollow shaft that extends from the first body part through the second body part and the thermally insulating material provided therein, and that may freely accommodate a connection portion 52 for the support heater 50. The bottom wall may include or be connected to a cylinder jacket-shaped, outwardly extending protrusion or drive shaft that is centered on the rotation axis L, and that has an outer diameter that is significantly smaller than the outer diameter of the body part. The drive shaft may define a passage that provides access to the interior of the body of the cylindrical container 36. More information with respect to a substrate support with a drive shaft may be derived from U.S. Pat. No. 9,018,567 incorporated herein by reference.

The substrate support assembly 30 may further include the support heater 50. The support heater 50 may comprise a heat generating portion. The connection portion 52 may have an elongate or straight shape with a first, lower end and a second, upper end. It may freely extend upward through the hollow shaft. Where the second, upper end of the connection portion 52 clears the shaft, it may be connected to the heat generating portion of the support heater 50. The heat generating portion may be substantially planar, and extend in a plane beneath, adjacent to and parallel to the support surface 34, and preferably cover an area that is substantially equal to an area of the support surface 34. In a preferred embodiment, the heat generating portion of the support heater 50 may include an electrically resistive heater, such as a (planar) heating spiral a central point of which may be connected to the second end of the connection portion 52 for electrical power.

The support assembly 30 may also include a base, which in the depicted vertical furnace 1 may include the doorplate 42 of the furnace. The substrate support 32 may be rotatably mounted on this base 42 by means of a bearing 44. The bearing 44 may preferably connect to the substrate support 32 at a lower end thereof (i.e., an end distal to the substrate support surface 34), such that the bearing 44 is disposed substantially below the substrate support 32 and it is shielded from a process atmosphere to which substrates 28 supported on the support surface 34 are to be subjected. In the depicted embodiment, the bearing 44 engages the drive shaft protrusion that extends from the bottom wall of the container 36. The first, lower end of the connecting portion 52 may be fixedly/non-rotatably attached to the base 42. In an embodiment, the support heater 50 may be self-supporting in the sense that, apart from its connection portion 52 connecting to the base 42, there is no external physical support to ensure that it maintains its position or configuration. The support heater 50 does in particular not mechanically contact the rotatably mounted substrate support 32.

A motor drive may be provided to rotate the substrate support 32 relative to the base 42 around its central axis L, and thus around the connection portion 52 of the support heater 50. Accordingly, a substrate carrier 24 disposed on top of the support surface 34 and holding one or more wafers 28 may be rotated relative to heating means 18 and relative to the support heater 50 to average out the effects that non-uniformities in the heating profile of the heating means 18 and heat generating portion of the support heater 50 may have on the wafers.

In order to optimize the temperature uniformity of the lower wafers further, support heater 50 may comprise more than one zone, the heat generating portion of each zone extending over only a part of the substrate support surface 34. E.g., a first zone may extend over a central region of support surface 34 and a second zone may extend over an outer region of support surface 34. In another embodiment a first zone may extend over a first tangentially extending region of support surface 34 and a second zone may extend over a second tangentially extending region of support surface 34. Each zone comprises two leads in the connecting portion 52.

Although illustrative embodiments of the present invention have been described above, in part with reference to the accompanying drawings, it is to be understood that the invention is not limited to these embodiments. Variations to the disclosed embodiments can be understood and effected by those skilled in the art in practicing the claimed invention, from a study of the drawings, the disclosure, and the appended claims.

Reference throughout this specification to “one embodiment” or “an embodiment” means that a particular feature, structure or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, the appearances of the phrases “in one embodiment” or “in an embodiment” in various places throughout this specification are not necessarily all referring to the same embodiment. Furthermore, it is noted that particular features, structures, or characteristics of one or more embodiments may be combined in any suitable manner to form new, not explicitly described, embodiments. 

The invention claimed is:
 1. A method, comprising: providing a substrate processing apparatus comprising: a substrate support provided with a support surface for supporting a substrate or a substrate carrier thereon and a support heater, disposed below the support surface, that is constructed and arranged to heat the support surface, wherein the apparatus comprises a heat shield constructed and arranged to cover and shield the substrate support when no substrate or substrate carrier is on the support surface, wherein the heat shield at least partially forms a chamber constructed and arranged to store the substrate support therein; exchanging at least one substrate of the substrate carrier, while covering the substrate support with the heat shield while heating the support surface of the substrate support with the support heater; moving the substrate support and the heat shield with respect to each other so as to support the substrate carrier on the support surface; and, moving the substrate in the substrate carrier into a reactor.
 2. The method according to claim 1, wherein the heat shield is separately and independently moveable relative to the support surface of the substrate support.
 3. The method according to claim 1, wherein the apparatus comprises a recess which can be closed with the heat shield to form the chamber constructed and arranged to store the substrate support therein.
 4. The method according to claim 1, wherein the chamber is substantially airtight.
 5. The method according to claim 1, wherein the shield comprises thermally insulating material thermally insulating the substrate support.
 6. The method according to 1, wherein the shield comprises an upper shield and a cylindrical side shield, which shields are interconnected to define a generally cylindrical chamber to cover and shield the substrate support when no substrate or substrate carrier is on the support surface.
 7. The method according to claim 1, wherein the apparatus comprises an actuator constructed and arranged to move at least one of the heat shield and the substrate support with respect to each other so as to move the cover to shield the substrate support when no substrate or substrate carrier is on the support surface.
 8. The method according to claim 7, wherein the apparatus comprises an elevator constructed and arranged to move the substrate support in a vertical direction.
 9. The method according to 1, wherein the substrate support comprises an upper plate, a cylindrical side plate and a bottom plate, which plates are interconnected to define a generally cylindrical container, wherein an outer surface of the upper plate defines the support surface of the substrate support, and wherein the container defines a body that extends between the upper plate and the bottom plate, which body accommodates at least part of the support heater.
 10. The method according to claim 9, wherein the body of the cylindrical container further accommodates thermally insulating material and wherein a heat generating portion of the heater is disposed adjacent the upper plate, and wherein the thermally insulating material is disposed below the heat generating portion of the support heater.
 11. The method according to claim 10, wherein the heat generating portion rests on the thermally insulating material.
 12. The method according claim 1, further comprising a reaction chamber defining a reaction space and an opening via which the support assembly is at least partly receivable in said reaction chamber, such that a substrate or substrate carrier supported thereon is receivable in the reaction space.
 13. The method according to claim 12, wherein the apparatus is a vertical thermal furnace; wherein the reaction chamber is at least partly formed by a bell jar-shaped reaction tube, and wherein the substrate support is at least partly receivable in said reaction tube via the opening at the lower end thereof, such that the support assembly, in a received state, substantially closes off said opening of the reaction tube.
 14. The method according to claim 1, further comprising a substrate carrier connected to the support surface of the substrate support and that is configured to hold at least one substrate. 